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=head1 NAME |
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|
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Coro - coroutine process abstraction |
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|
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=head1 SYNOPSIS |
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|
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use Coro; |
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|
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async { |
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# some asynchronous thread of execution |
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}; |
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|
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# alternatively create an async coroutine like this: |
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|
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sub some_func : Coro { |
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# some more async code |
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} |
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|
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cede; |
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|
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=head1 DESCRIPTION |
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|
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This module collection manages coroutines. Coroutines are similar to |
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threads but don't run in parallel. |
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|
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In this module, coroutines are defined as "callchain + lexical variables |
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+ @_ + $_ + $@ + $^W + C stack), that is, a coroutine has it's own |
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callchain, it's own set of lexicals and it's own set of perl's most |
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important global variables. |
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|
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=cut |
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|
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package Coro; |
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|
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use strict; |
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no warnings "uninitialized"; |
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|
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use Coro::State; |
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|
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use base qw(Coro::State Exporter); |
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|
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our $idle; # idle handler |
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our $main; # main coroutine |
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our $current; # current coroutine |
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|
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our $VERSION = '3.01'; |
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|
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our @EXPORT = qw(async cede schedule terminate current unblock_sub); |
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our %EXPORT_TAGS = ( |
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prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)], |
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); |
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our @EXPORT_OK = @{$EXPORT_TAGS{prio}}; |
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|
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{ |
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my @async; |
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my $init; |
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|
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# this way of handling attributes simply is NOT scalable ;() |
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sub import { |
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no strict 'refs'; |
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|
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Coro->export_to_level (1, @_); |
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|
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my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE}; |
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*{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub { |
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my ($package, $ref) = (shift, shift); |
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my @attrs; |
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for (@_) { |
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if ($_ eq "Coro") { |
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push @async, $ref; |
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unless ($init++) { |
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eval q{ |
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sub INIT { |
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&async(pop @async) while @async; |
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} |
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}; |
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} |
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} else { |
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push @attrs, $_; |
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} |
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} |
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return $old ? $old->($package, $ref, @attrs) : @attrs; |
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}; |
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} |
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|
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} |
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|
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=over 4 |
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|
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=item $main |
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|
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This coroutine represents the main program. |
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|
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=cut |
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|
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$main = new Coro; |
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|
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=item $current (or as function: current) |
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|
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The current coroutine (the last coroutine switched to). The initial value |
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is C<$main> (of course). |
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|
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This variable is B<strictly> I<read-only>. It is provided for performance |
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reasons. If performance is not essentiel you are encouraged to use the |
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C<Coro::current> function instead. |
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|
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=cut |
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|
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# maybe some other module used Coro::Specific before... |
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$main->{specific} = $current->{specific} |
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if $current; |
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|
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_set_current $main; |
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|
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sub current() { $current } |
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|
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=item $idle |
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|
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A callback that is called whenever the scheduler finds no ready coroutines |
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to run. The default implementation prints "FATAL: deadlock detected" and |
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exits, because the program has no other way to continue. |
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|
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This hook is overwritten by modules such as C<Coro::Timer> and |
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C<Coro::Event> to wait on an external event that hopefully wake up a |
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coroutine so the scheduler can run it. |
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|
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Please note that if your callback recursively invokes perl (e.g. for event |
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handlers), then it must be prepared to be called recursively. |
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|
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=cut |
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|
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$idle = sub { |
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require Carp; |
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Carp::croak ("FATAL: deadlock detected"); |
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}; |
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|
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# this coroutine is necessary because a coroutine |
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# cannot destroy itself. |
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my @destroy; |
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my $manager; $manager = new Coro sub { |
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while () { |
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# by overwriting the state object with the manager we destroy it |
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# while still being able to schedule this coroutine (in case it has |
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# been readied multiple times. this is harmless since the manager |
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# can be called as many times as neccessary and will always |
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# remove itself from the runqueue |
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while (@destroy) { |
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my $coro = pop @destroy; |
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$coro->{status} ||= []; |
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$_->ready for @{delete $coro->{join} || []}; |
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|
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# the next line destroys the coro state, but keeps the |
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# coroutine itself intact (we basically make it a zombie |
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# coroutine that always runs the manager thread, so it's possible |
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# to transfer() to this coroutine). |
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$coro->_clone_state_from ($manager); |
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} |
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&schedule; |
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} |
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}; |
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|
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# static methods. not really. |
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|
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=back |
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|
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=head2 STATIC METHODS |
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|
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Static methods are actually functions that operate on the current coroutine only. |
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|
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=over 4 |
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|
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=item async { ... } [@args...] |
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|
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Create a new asynchronous coroutine and return it's coroutine object |
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(usually unused). When the sub returns the new coroutine is automatically |
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terminated. |
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|
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Calling C<exit> in a coroutine will not work correctly, so do not do that. |
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|
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When the coroutine dies, the program will exit, just as in the main |
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program. |
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|
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# create a new coroutine that just prints its arguments |
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async { |
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print "@_\n"; |
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} 1,2,3,4; |
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|
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=cut |
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|
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sub async(&@) { |
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my $pid = new Coro @_; |
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$pid->ready; |
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$pid |
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} |
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|
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=item schedule |
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|
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Calls the scheduler. Please note that the current coroutine will not be put |
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into the ready queue, so calling this function usually means you will |
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never be called again unless something else (e.g. an event handler) calls |
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ready. |
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|
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The canonical way to wait on external events is this: |
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|
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{ |
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# remember current coroutine |
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my $current = $Coro::current; |
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|
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# register a hypothetical event handler |
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on_event_invoke sub { |
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# wake up sleeping coroutine |
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$current->ready; |
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undef $current; |
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}; |
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|
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# call schedule until event occured. |
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# in case we are woken up for other reasons |
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# (current still defined), loop. |
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Coro::schedule while $current; |
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} |
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|
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=item cede |
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|
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"Cede" to other coroutines. This function puts the current coroutine into the |
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ready queue and calls C<schedule>, which has the effect of giving up the |
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current "timeslice" to other coroutines of the same or higher priority. |
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|
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=item terminate [arg...] |
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|
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Terminates the current coroutine with the given status values (see L<cancel>). |
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|
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=cut |
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|
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sub terminate { |
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$current->cancel (@_); |
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} |
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|
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=back |
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|
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# dynamic methods |
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|
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=head2 COROUTINE METHODS |
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|
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These are the methods you can call on coroutine objects. |
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|
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=over 4 |
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|
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=item new Coro \&sub [, @args...] |
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|
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Create a new coroutine and return it. When the sub returns the coroutine |
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automatically terminates as if C<terminate> with the returned values were |
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called. To make the coroutine run you must first put it into the ready queue |
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by calling the ready method. |
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|
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Calling C<exit> in a coroutine will not work correctly, so do not do that. |
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|
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=cut |
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|
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sub _run_coro { |
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terminate &{+shift}; |
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} |
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|
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sub new { |
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my $class = shift; |
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|
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$class->SUPER::new (\&_run_coro, @_) |
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} |
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|
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=item $success = $coroutine->ready |
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|
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Put the given coroutine into the ready queue (according to it's priority) |
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and return true. If the coroutine is already in the ready queue, do nothing |
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and return false. |
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|
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=item $is_ready = $coroutine->is_ready |
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|
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Return wether the coroutine is currently the ready queue or not, |
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|
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=item $coroutine->cancel (arg...) |
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|
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Terminates the given coroutine and makes it return the given arguments as |
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status (default: the empty list). |
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|
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=cut |
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|
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sub cancel { |
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my $self = shift; |
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$self->{status} = [@_]; |
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push @destroy, $self; |
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$manager->ready; |
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&schedule if $current == $self; |
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} |
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|
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=item $coroutine->join |
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|
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Wait until the coroutine terminates and return any values given to the |
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C<terminate> or C<cancel> functions. C<join> can be called multiple times |
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from multiple coroutine. |
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|
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=cut |
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|
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sub join { |
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my $self = shift; |
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unless ($self->{status}) { |
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push @{$self->{join}}, $current; |
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&schedule; |
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} |
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wantarray ? @{$self->{status}} : $self->{status}[0]; |
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} |
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|
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=item $oldprio = $coroutine->prio ($newprio) |
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|
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Sets (or gets, if the argument is missing) the priority of the |
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coroutine. Higher priority coroutines get run before lower priority |
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coroutines. Priorities are small signed integers (currently -4 .. +3), |
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that you can refer to using PRIO_xxx constants (use the import tag :prio |
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to get then): |
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|
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PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN |
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3 > 1 > 0 > -1 > -3 > -4 |
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|
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# set priority to HIGH |
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current->prio(PRIO_HIGH); |
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|
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The idle coroutine ($Coro::idle) always has a lower priority than any |
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existing coroutine. |
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|
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Changing the priority of the current coroutine will take effect immediately, |
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but changing the priority of coroutines in the ready queue (but not |
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running) will only take effect after the next schedule (of that |
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coroutine). This is a bug that will be fixed in some future version. |
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|
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=item $newprio = $coroutine->nice ($change) |
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|
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Similar to C<prio>, but subtract the given value from the priority (i.e. |
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higher values mean lower priority, just as in unix). |
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|
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=item $olddesc = $coroutine->desc ($newdesc) |
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|
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Sets (or gets in case the argument is missing) the description for this |
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coroutine. This is just a free-form string you can associate with a coroutine. |
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|
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=cut |
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|
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sub desc { |
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my $old = $_[0]{desc}; |
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$_[0]{desc} = $_[1] if @_ > 1; |
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$old; |
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} |
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|
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=back |
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|
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=head2 UTILITY FUNCTIONS |
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|
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=over 4 |
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|
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=item unblock_sub { ... } |
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|
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This utility function takes a BLOCK or code reference and "unblocks" it, |
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returning the new coderef. This means that the new coderef will return |
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immediately without blocking, returning nothing, while the original code |
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ref will be called (with parameters) from within its own coroutine. |
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|
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The reason this fucntion exists is that many event libraries (such as the |
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venerable L<Event|Event> module) are not coroutine-safe (a weaker form |
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of thread-safety). This means you must not block within event callbacks, |
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otherwise you might suffer from crashes or worse. |
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|
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This function allows your callbacks to block by executing them in another |
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coroutine where it is safe to block. One example where blocking is handy |
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is when you use the L<Coro::AIO|Coro::AIO> functions to save results to |
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disk. |
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|
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In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when |
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creating event callbacks that want to block. |
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|
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=cut |
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|
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our @unblock_pool; |
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our @unblock_queue; |
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our $UNBLOCK_POOL_SIZE = 2; |
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|
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sub unblock_handler_ { |
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while () { |
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my ($cb, @arg) = @{ delete $Coro::current->{arg} }; |
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$cb->(@arg); |
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|
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last if @unblock_pool >= $UNBLOCK_POOL_SIZE; |
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push @unblock_pool, $Coro::current; |
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schedule; |
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} |
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} |
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|
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our $unblock_scheduler = async { |
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while () { |
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while (my $cb = pop @unblock_queue) { |
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my $handler = (pop @unblock_pool or new Coro \&unblock_handler_); |
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$handler->{arg} = $cb; |
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$handler->ready; |
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cede; |
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} |
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|
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schedule; |
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} |
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}; |
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|
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sub unblock_sub(&) { |
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my $cb = shift; |
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|
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sub { |
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push @unblock_queue, [$cb, @_]; |
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$unblock_scheduler->ready; |
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} |
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} |
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|
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=back |
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|
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=cut |
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|
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1; |
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|
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=head1 BUGS/LIMITATIONS |
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|
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- you must make very sure that no coro is still active on global |
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destruction. very bad things might happen otherwise (usually segfaults). |
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|
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- this module is not thread-safe. You should only ever use this module |
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from the same thread (this requirement might be losened in the future |
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to allow per-thread schedulers, but Coro::State does not yet allow |
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this). |
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|
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=head1 SEE ALSO |
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|
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Support/Utility: L<Coro::Cont>, L<Coro::Specific>, L<Coro::State>, L<Coro::Util>. |
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|
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Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>. |
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|
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Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::Select>. |
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|
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Embedding: L<Coro:MakeMaker> |
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|
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=head1 AUTHOR |
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|
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Marc Lehmann <schmorp@schmorp.de> |
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http://home.schmorp.de/ |
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|
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=cut |
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|